1. Field of the Invention
The present invention relates to technology for forming an electrical path through an insulating layer.
2. Description of the Background Art
It is often desirable to electrically ground a substrate through an insulating layer on its surface. The substrate may be, for example, a silicon wafer or other semiconductor substrate. The insulating layer may be, for example, an oxide or nitride layer on a surface of the substrate.
For example, in an electron beam inspection apparatus, a mechanism is typically used to ground a silicon wafer being inspected through its backside, where the backside is the side away from the integrated circuitry being manufactured. The conventional mechanism presses sharp pins of a hard metal against the insulating layer on the wafer backside to force electrical conduction paths from the pins to the bulk silicon wafer by either mechanical destruction of the insulating layer under the pins, or electrical arcing from the pins through the insulating layer, or a combination of both.
Unfortunately, this conventional mechanism causes irreversible damage (electrical and/or mechanical) to the wafer backside. For example, an oxide layer on the backside of a silicon wafer may be scratched, or otherwise mechanically damaged by the sharp grounding pins, so as to expose the bulk silicon. Subsequently, as the wafer continues in the fabrication process, an etch process may be applied that inadvertently and undesirably etches the exposed silicon on the backside. In addition, if the oxide layer is very thick, the mechanical damage may be substantial enough to cause debris particles near the damaged area that may introduce misalignment of the wafer.